In order to detect the start of the 2 Mbit/s signal
and thereby the start of the customers data, The V5 byte must be seen be the distant end. This is achieved
by adding four overhead bytes to the multiframe, which together form a
calculated byte count to the start of V5. This is called a pointer value and is known as the TU Pointer.

There are four
pointer bytes called V1, V2, V3 and V4, which are used to calculate the
location of V5.